Money for top ups gone astray

Upzeecreek

Made a payment via HMRC app early March for pension top ups. It's done via open banking and the app takes you to your bank account to pay and authorise. 
HMRC say they have no record of the money being paid despite me receiving a confirmation email with an 18 digit reference number. 
It's been referred to their back office for investigation but still rather worrying that 6.5 k has disappeared into the ether! 
Just wondering if this has happened to anyone else? 

Lesley5

Hi,
I paid nearly £6k but only £3.5 was credited.
I await a callback 🤞